I am a learner in MVC, I am facing a issue in passing data, I want to pass a data from one view to another view in MVC, How can I do this? help me,
I will select the firstname in one view and I want to pass the firstname to another view?
Views don't communicate with other views.
Consider this illustration from the Wikipedia page:
A view doesn't connect to another view. It is simply an interface presented to the user. Data which originates in a view (such as user input) would then be passed to a controller, which in turn directs (controls) the data/logic flow of the application. (Not the logic itself, the flow of the logic.)
That controller will then interact with the models (if necessary, sometimes the only action for a controller to perform is to immediately render another view, such as a redirect in a web application) and present the next view.
If data sent to the controller is needed in the next view, it would be the responsibility of the controller to include it in the next view.
Related
Following this article There are two schools of thought with regard to whether the View interacts directly with the Model or not.
I'm interested in the case where View don't interact with Model. If only Controller knows about View but not View knows about Controller we can easily update View with Model data (write some text, for ex.) by calling View and Model methods in Controller.
But how could Controller and Model react to View changes (button push, for ex.) if View don't know about Controller or Model?
-One solution-
One way to make 2 objects communicate with loose coupling (in your case views don't know about controller and vice-versa) it to use a "messenger" pattern.
The 'messenger' is an object known by all the others. Using the 'messenger' object:
You register objects (your views) to send messages
You register objects (controlers, models...) to listen to specific messages
In this way, a model can react to a specific view's event because it is registered into the messenger.
There is a full example here (C# code):
Light messenger pattern
Tell me if it s what you were looking for...
I was going through the articles describing the MVC pattern. None of them were clear on explaining the role of Controller in MVC. Some says Controller can make changes to the view such as disabling a button or changing the text color whereas some says any changes to the view should be done inside view only. Can you please give me tips on the following question?
1) Can any change pertaining to the view be done inside the controller?
2) What not should be written inside a controller?
3) It is right to say "View should do all the changes by itself when a new recordset is generated by the model, as the view queries model directly, and controller is not involved in this transaction?"
4) I have heard this statement about MVC "In current version of windows application development. View is capable to handle the event(like button press) and the controller is called when needed.It is stupid to delegate the event listening to the controller now." Doesn't this sound more like a MVP?
Thanks. Hoping to get some help here.
In my opinion:
1) The controller changes the data provided to the view, so in a way, yes. The view should just manage the presentation of the data provided to it by the controller.
2) The controller should contain all code to handle any actions taken by the user. Depending on the size of your application, the controller can hand the action off to a business layer to do the work then gather view data once the business layer is complete and hand it back to the view. Or, if you don't have a business layer, it can do the work directly.
3) In true MVC, the view should not have access to the model directly. The controller should create view objects from the model and pass them to the view. In any case, the view should never do any real work other than presentation.
4) I don't know MVP so cannot answer this question.
1) Controller responsibility is primarily "execute an action, choose an appropriate view, provide some data to that view and return the view to a user".
2) As MVC tries to separate presentation logic and UI rendering, I believe, controller shouldn't attempt to perform any of view responsibilities: listening to UI events or pre-formatting of values dateString = data.ToString('YYYY-MM') - that's all should go to view.
3) in MVC view knows all about a model - model is rendered by view without any controller involvement (that's primary 'issue' fixed by MVP, where view should and model should unbound as much as possible). However it's not recommended for view to query model directly. Instead, all data changes should be reported to view by model using Observer pattern.
Consider the following -
schema from wikipedia article - dashed line from model to view indicates that fact. Just keep in mind that model is more viewmodel here and shouldn't really be a part of BL layer.
So here scenario could be the following:
User clicks "add item"
View sends request to the controller with the item data
Controller makes call to BL, which makes changes to the model (adds new item to the list).
Model fires "updated" event to the view (or "error" event, if there are some issues in underlying layers)
View updates UI according to changes reported.
4) The statement is perfectly true. In MVC you shouldn't do that. I assume, in MVP you shouldn't do that as well - I mean, listening to events from UI directly. That should be done either by forwarding event by view; or using a platform-independent view representation, like
inderface IMyGridView
{
event ItemEvent AddItemClick;
}
(which doesn't make sense for MVC, as view is pretty much independent from a controller and mostly all view actions are result in calls to controller).
I've been tasked with converting an existing webforms application to mvc 3 razor.
The application currently has an aspx page which has a static header user control and "n" amount of other user controls which are dynamically created. In the code behind for the file, it is executing the below code in various specific sections to dynamically process user controls with information provided from the database.
I know how to statically create partial views, but being somewhat new to MVC, how would I go about defining this new "aspx" page and also to dynamically find, load and add the partial views (each equivalent to the below webforms code)?
btw, the code will be in C# as well.
Dim parent As Control = Page.FindControl(_moduleSettings.PaneName)
Dim portalModule As PortalModuleControl = CType(Page.LoadControl(_moduleSettings.DesktopSrc), PortalModuleControl)
parent.Controls.Add(portalModule)
I think I can do something like this when the page is rendering. I want to make it as simple as possible.
The "PaneName" will be set in the parent variable which determines where in the page it will be shown (Left, Right, or Main)
The "DeskTopSrc" is the name of the partial view to display.
So, take the code out of the code behind and place it in the main View. Perform the above processing logic in the View (boy, switching from aspx code behind to a View throws me a loop. I gotta get use to doing the processing in the View. Reminds me of Classic ASP, but the Razor syntax will help).
Display the partial view via the #Html.PartialView('partial view name'). This view might have a grid in it associated with a specific model.
Below is the part I am unsure about.
I've done database processing for a main View associated with a Controller, but not with a partial view that needs to do some database processing.
Perform any database processing logic (if any) for this partial view in the Controller associated with the main View (which contains this partial View).
In the Action Index method while looping over these "partial views", I can get the data and display the views....
Ahhh, I think I got it.....
After carefully thinking it through, if someone could help me out with the last statement here, I would greatly appreciate it.
1.Have partial views already statically created with the specific HTML markup that I need in the Views/Shared folder.
2.In the main View, I will already have
#Html.Partial(ViewData["partial_view_left"])
#Html.Partial(ViewData["partial_view_right"])
#Html.Partial(ViewData ["partial_view_main"])
statements in specific locations of the HTML which will render the partial views as I retrieve their names from the database.
3.In the Controller's Index method, I need to do the following:
a) Loop through the converted logic (from the CodeBehind of the existing WebForms page in the PageLoad event) in the Index action method of the new Controller which will load the partial views dynamically.
1) Find out where the partial view will be displayed (left, right, main) from the database via the "parent" variable.
2) Find out the name of the partial view that will be displayed from the database via the “DesktopSrc” variable.
eg: ViewData["partial_view_left"] = "left_view"; OR
ViewData["partial_view_right"] = "right_view"; OR
ViewData["partial_view_main"] = "main_view";
3) Right here is where I am unsure of how to properly display the partial view.
I need to have the equivalent of a webforms "Controls.Add" method to render each partial view from the Controller that I retrieve from
the database from step 3.a.2
What statement can I use in this Index method of the Controller that will accomplish this?
In other words, if I dynamically need to display several partial views inside of a parent view, how is this accomplished in MVC?
I know for each partial view, I can send over the model associated with it, but I just don't know how I can place several partial views inside the main view page at run time from one Action method.
If your partial views need to do some processing, like database retrieval, then you should use
#{Html.RenderAction("ActionName");}
This will call an action method (which doesn't have to be on the same controller) that can dynamically choose a view based on logic, and populate the ViewModel with data from the database.
public ActionResult ActionName()
{
var modelData = GetData();
return View(settings.DesktopSrc, modelData);
}
I'm trying to understand MVC.
Let's say on the View I have a checkbox, we'll call it 'checkBox1'...
In my Controller, can I access this checkbox directly?
Can I go:
checkBox1.Checked = true
??
A controller cannot directly access the elements of a view as it has no information about it. A controller can only act as a point of control to regulate data between the views and models. However you can manipulate the views from the controller like loading a specific view template or rendering a chunk of code ( in case of xhr request) to the output. But once it renders that it will not have any information about the individual elements of the view.
Take a look at this
http://www.enode.com/x/markup/tutorial/mvc.html
No. The controller deals with the data (model) sent to and from the view and is deliberately separated from the details of the View.
I suggest spending some time reading up on the basics of ASP.NET MVC and doing some tutorials on the ASP.NET MVC site
Read here for details on handling checkboxes...
CheckboxList in MVC3.0
In MVC pattern where does the response.redirect will come.Either in view and controller.
I'd also say in the controller. the view is only responsible for displaying the data and maybe doing a little data fetching. Although I'm restricting my views to just displaying and formatting.
So the controller has all the information when to redirect. So the result of a controller action is either a redirect or a view rendering. (Where presenting a download is considered as view rendering)
Must be in Controller.
Controller's name suggested that every control statement must come in the Controller.
View is responsible for the Design code only.
It will definitely come in controller.